You are asking about old klein (before 95) or "Treklein" (made after 95).
Now, all aluminium bikes use technology created by klein and Cannondale (Cunningham……
). So, actually, a klein or a Cannondale seems so ordinary.
If you see the prices on ebay, it's not modern Attitude who are going around 2000$, but all the mythics models : for exemple a 1990 or 1991, Team america Attitude (the neon green-white-pink model).
Take a time machine and go to the end of the 80ies and to the beginning of the 90ies : no suspension, titanium was very very rare, and a lot of heavy steel bikes every where… and… the first aluminum oversized : whaouh ! It was something new, original, fantastic. They were pioneers and all things had to be created for mountain biking. Cannondale, Klein, Merlin… were more "craftsmen" than the actual big plant who are welding they frame in Asia…
Buying an old Attitude is buying a piece of history. Riding an Attitude is discover feelings forgotten since a very long time.
I still ride my Attitude, and my Singlespeed Pinnacle. I love them because, it's "no compromise" bike
: It's only "on/off". They give what you give, and for working the riding technic, they are a very good school.
I love titanium (and steel) bike too. But it's really a too different philosophy. If I want more confort and if I need to go far and for longtime, I prefer my Merlin
But, I admit that 2000$ is really too expensive for an old Klein. Ebay is a stupidity, and don't give a good idea of the prices.
My Attitude cost to me around 1000 euros, and my Pinnacle fuselage (steel fork and MC1 combo) cost me 300 euros, and I have bought them on Retrobike, in a lucky time I could pay them. But when I see actual bike price, I think it's not so crazy for bikes who haunt my nights since the begining of 90ies. When I look them in my garage or when I ride them, sure I don't regret.
Well… it's really not acceptable…